Advances in wireless communication have revolutionized the way we communicate and access information, and has birthed a plethora of wireless capable consumer devices whose affordability and availability have increased over time. Generally, wireless capable consumer devices may communicate with other wireless capable devices by exchanging radio frequency (RF) communication signals via a transceiver, which may be located internally or externally to the device. In many cases, transceiver output power directly impacts wireless performance, with higher transceiver output power limits allowing the wireless device to achieve greater throughput and/or broader wireless coverage (e.g., enhanced coverage areas).
However, RF transmissions may produce RF radiation, e.g., electromagnetic radiation in the frequency range of about three kilohertz (kHz) to about 300 Gigahertz (GHz), which may be harmful to humans at elevated exposure/absorption thresholds. Consequently, the Federal Communications Commission (FCC) has regulated the RF radiation output of various wireless devices to limit the general public's exposure to RF radiation. Some of the FCC's regulations and/or compliance standards may be outlined in Institute of Electrical and Electronics Engineers (IEEE)/American National Standards Institute (ANSI) publication C95.1-1992 entitled “Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 khz to 300 GHz” and IEEE/ANSI C95.3-2002 entitled “Recommended Practice for Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave”, both of which are incorporated by reference herein as if reproduced in their entirety. Specifically, the FCC regulations specify maximum Specific Absorption Rates (SAR) for various RF devices based on different factors. SAR is defined as the rate of RF energy absorption per unit mass at a point in an absorbing body, and may be calculated by the formula:
            S      ⁢                          ⁢      A      ⁢                          ⁢      R        =                  σ        ·                  E          2                    ρ        ,where σ is the conductivity of the tissue simulating material in Siemens per meter (S/m), E is the total root mean squared (RMS) electric field strength in volts per meter (V/m), and ρ is the mass density of the tissue-simulating material in kilograms per cubic meter (kg/m3). To comply with these regulations, some wireless terminal devices, e.g., universal serial bus (USB) data-cards, wireless routers, tablets, electronic readers (e-readers), phones, etc., must be submitted to a certified testing laboratory for SAR compliance evaluation.
RF radiation levels may be related to both transceiver output power and separation distance (i.e., the distance separating the human body and the RF radiation source), as well as other factors (e.g., shielding, antenna design, etc.). Specifically, the amount of RF radiation absorbed by a human body may increase when transceiver output power increases, as well as when the separation distance decreases. Consequently, one strategy for satisfying SAR compliance criteria may be to reduce transceiver output power to offset a reduction in separation distance (e.g., lowering output power as the human body approaches RF radiation source). For instance, some wireless devices (e.g., cell phones) may employ touch screen sensors to detect the presence of a human body. However, touch screen sensors may require direct human body contact, and therefore may be incapable of proximity detection (i.e., approximating the distance of the human body to the RF radiation source) and may be ill-suited for wireless devices. Alternatively, optical or infrared proximity detection may detect the presence (as well as approximate the separation distance) of an object using electromagnetic radiation (e.g., by bouncing RF waves or optical beams off the object). However, optical/infrared proximity detection may be incapable of differentiating between human bodies and inanimate objects (e.g., books, tables, etc.), and consequently may decrease wireless performance by frequently detecting false positives (i.e., by reducing transceiver output power when doing such is not necessary to satisfy SAR compliance criteria). For instance, optical/infrared proximity detection may trigger a decrease in transceiver output power upon detecting an inanimate object (e.g., table). As such, an improved method for accurately detecting the presence and proximity of a human body is desired to better optimize wireless performance while satisfying SAR compliance criteria.